This invention relates to a heat transfer film, more particularly to a heat transfer film, which can simplify the structure of a printer by providing specific detection marks in said heat transfer film.
In the prior art, as a method for forming a color image according to the heat transfer method, there has been practiced the heat transfer method by use of a lengthy heat transfer film having a large number of unit heat transfer layers comprising colored heat transfer layers of, for example, yellow, magenta and cyan (and black, if necessary) provided on a continuous base film.
These lengthy heat transfer films may be classified broadly into (a) the lengthy heat transfer films of the so-called wax type of which heat transfer layers are softened to be thermally transferred in the shape of images onto a heat transferable material, and (b) those of the so-called sublimation type in which the dyes in the heat transfer layers are sublimated (thermally migrated), whereby only the dyes are thermally transferred in the shape of images onto the heat transferable material.
In either type, the above unit heat transfer layers are provided on the continuous base film in a large number of units of 50 to 100, and the film is stored and used as wound into a roll.
When such color images are formed by a printer by use of these heat transfer films, since it is required to allow a printer to detect that heat transfer has been effected in a predetermined order on the heat transferable material (i.e., material to be heat transferred), for example, in the order of yellow, magenta, cyan and black, and what color is existing at the printing portion, detection marks having such information and functions are commonly formed in any region of the heat transfer film.
As a method for allowing a printer to detect such detection marks, the method as shown in FIG. 6 and FIG. 7 has been practiced.
More specifically, in the case shown in FIG. 6, a projector 6 is provided within a printer, while a light receiving sensor 7 is provided on the opposite side to the heat transfer film 10, and by moving the heat transfer film 10, partial interception of the detection light 8 from the projector 6 is detected by the detection mark 3 comprising a light absorbing layer of a different color and existing on the heat transfer film to determine the position of the heat transfer film 10 and the hue of the heat transfer layer.
The method shown in FIG. 7 is practiced by providing a projector 6 and a light receiving sensor 7 on one side of the heat transfer film 10 having the same detection mark 3 and a reflective plate 9 on the other side. In this case, the position and the hue of the heat transfer film 10 are detected by the presence or the absence of the reflected light 11.
The printers generally used in the above heat transfer system are becoming progressively miniaturized and therewith, simplification of circuit wiring and improvement of detection precision, and the like of the detection mark have been demanded. However, in the system of the prior art shown in FIG. 6, since a projector and a light receiving sensor are arranged on both sides of the heat transfer film, it cannot respond to the need for miniaturization of the device.
On the other hand, although the system of FIG. 7 can be miniaturized to some extent, a reflective plate is desired to be provided on the opposite side, which cannot be said to be satisfactory for miniaturization and simplification.
Also, in both of the systems of the prior art, when the heat transfer film is cut during printing, cutting cannot be detected, resulting in problems such as generation of bad images or jamming of the heat transfer film.
Accordingly, an object of the present invention is to provide a heat transfer film which requires no complicated detection mechanism and which can also immediately detect cutting of the heat transfer film as well as the film information, such as the position and hue of the heat transfer layer.